Hrm...maybe I should clarify.

The second you swapped in the b18b integra engine, you were put in street modified. Basically an engine swap from a different car will put you in SM. Street modified is a tough class because they allow for massive weight reductions. Unless you do some serious weight reduction you probably won't be competitive, but it's all for the learning anyways.

I run in STS...basic bolt-on mods, suspension, no weight reduction, BONE-STOCK engine internals (no cams, forced induction, etc.). If you still had your stock civic engine (with no internal modifications) you would also be running in STS. STS is a pretty "tame" class...since most modifications are restricted to bolt-ons you don't see crazy gutted out racers.

I wouldn't worry about it too much, just go out and have fun. Most hard-co autocrossers will tell you to stay stock as long as possible and only add modifications when you've reached a plateau, but I know its tough to resists adding on modifications.

Shingo